Portable demagnetizer



Jan. 25, 1938. I J, BEECHLYILJ 2,106,233

PORTABLE DEMAGNETIZER Filed Sept. 21, 1936 2 Sheets-Sheet l 3 UZQW a 526 "L 9 1; x 000 1 J3 yf m J9 J6 J0 jg c/ofinZ' Beecklyza UDO Jan. 25, 1938. .1. T. BEECHLYN 2,106,233

PORTABLE DEMAGNET I ZER Filgd Sept. 21', 1936 2 Sheets-Sheet 2 \fi-w-i g 6 V&

59. @f I jrldemdv" Patented Jan. 25, 1938 UNITED STATES PATENT OFFICE 0. S. Walker 00. Inc.

, Worcester, Mass, a corporation of Massachusetts 7 Application September 21, 1936, Serial No. 101,773

10 Claims.

The principal object of this invention is to provide improved means for demagnetizing articles of high carbon or alloy steels which, during their process of manufacture, have been held by mag- 6 netic chucking.

More specifically the objects of this invention are to provide a light weight portable device of this nature which will be powerful in action and can be manually applied to work that is too large for convenient handling in relation to stationary means of demagnetization; to provide a cored device of this type having a strong external magnetic field combined with means for obtaining a rolling engagement with the surface to be treated, whereby the friction, ordinarily encountered with cored demagnetizers through magnetic attraction, is largely avoided; to provide a device capable of good working engagement with a variety of surface contours, including cylinders and cones, whether external or internal, such as for example larger roller bearing races; to provide an operating range of field intensity wherein the gradient will not be abrupt, with the object of enhancing the allowable rate of passage of the work, when the device is energized by alternating current of ordinary commercial frequency, and to provide a device that will be well adapted for use either as a stationary or portable demagnetizing means.

Other objects and advantages of the invention will appear hereinafter.

Reference is to be had to the accompanying drawings, in which Fig. 1 is a central sectional view of a demagnetizer constructed in accordance with this invention;

Fig. 2 is a bottom plan view of the same, partly broken away and in section;

Fig. 3 is a longitudinal sectional view on the line 33 of Fig. 2;

Fig. 4 is an end view of the core body;

Fig. 5 is a plan of the same;

Fig. 6 is an end view of a modified construction which comes within the scope of this invention, shown partly in section, and

Fig. 7 is an end view of the same.

In demagnetizers of the cored type it has been customary to employ fiat pole plates of considerable area terminated abruptly in the working plane, the work being placed directly on the plate and withdrawn by a sliding action generally with considerable manual effort. It is evident that such a type of device is not well suited for easy demagnetization.

In the present device the flux is concentrated in a relative small pole area whereby the field outside the core is intensified to an extent permitting a space between the pole face and the working plane, the point of nearest approach being along a line in the center of the pole. This spacing and a receding contour of the pole faces on each side of the nearest approach tend to produce an easy slope in the field gradient, that permits complete demagnetization to be obtained with a relatively rapid passage of the work. A rolling engagement is provided which will, of course, greatly facilitate the operation.

In Figs. 1 to 5, which represent a preferred form of the device, a laminated core body I is shown having the general form of a large segment of a cylinder. Two deep recesses extend longitudinally in the core body whereby is formed a pole system of characteristic E type, with the tips of the poles 2 and 3, bounded by the segmental arc. Disposed within the recesses and surrounding the central pole is a suitable winding 4 designed for operation on alternating current. The coil is secured in position by means of clips 5 which also serve for clamping together the laminations of the central pole by means of tie rods 6 extending longitudinally through perforations in the laminations. Clamping of the laminations is obtained by two heading memhers I secured by ties 8. The clamping surfaces of the heading members are suitably recessed at 9 to accommodate the ends of the coil 4. The winding 4 is fed from a source of alternating current through a flexible cable 38.

Each of the heading members 1 carries a shaft like cylindrical extension I B, coaxial with the segmental arc of the core body I. Secured to the extreme ends of these extensions are frame members l I which are provided with lugs l2 for arbitrarily securing the device to a bench or other suitable foundation. Each of the frame members also carries two lateral extensions 13 and between the two pairs of these are secured handles H in. a position preferably parallel with the axis of the core body.

On the extensions Ill are rotatably mounted two roller heads [5. These are provided with a suitable bearing lining it, preferably of the wooden oil-less type. At their outer circumference the two heads are fitted to receive the ends of a cylindrical shell H, which has a length somewhat greater than the core body I. This cylinder together with its heads completely surrounds the magnetic element and serves at once to provide a rolling engagement with the surface of work passed across the device over the pole 2. Also til they provide an effective seal against the entrance of ferrous matter into the coil and core through magnetic attraction.

To prevent excessive eddy currents from arising by the passage of the alternating flux through the shell, the latter may be made from dielectric material, but, with consideration to strength, it has been found desirable to employ a metal having high electrical resistivity, such as can be obtained with certain manganese or nickel alloys.

In the form shown in Figs. 1 to 5 the shell is not directly secured to the roller heads but is kept in seated engagement on these through the action of leaf springs 18. These springs are affixed to the frame members H and exert a moderate axial pressure on thrust rings IS. The latter are thus urged from opposite sides against the bearing linings of the roller heads and thereby maintain the seated arrangement of the shell IT. This arrangement has been found a convenient method of construction and assembly and it also provides a certain amount of resiliency in cases where heavy work pieces are brought violently into contact with the cylinder 11.

With any method for demagnetizing materials having high magnetic retentivity the efiectiveness of the operation depends on an adequate degree of initial penetration by an alternating magnetic field and on the rate of subsidence of this penetration, i. e., with a material of given characteristics the decrement in induction in each of successive cycles, from that of the immediately preceding cycle, must not exceed a certain critical value. From which it follows that the period of stepping down must embrace, at least, a certain number of cycles.

The stepping down is usually efiected by gradually withdrawing the object from an intense portion of the field rather than by diminishing the field itself. With a given frequency of alternation an abrupt intensity gradient in the field will therefore necessitate a slower Withdrawal of the object. Conversely, an extended and uniform gradient, such as I employ, will permit a relatively rapid passage of the object.

When the device is used as a portable tool it is manipulated by the handles, ordinarily in a position inverted from that shown in the drawings and simply rolled over the surface to be treated. The use of the demagnetizer in its portable form permits a new procedure. The device can be applied directly to the article to be demagnetized, before it is removed from a magnetic chuck, thereby avoiding a second handling of the article. In the case of hardened steel it will entirely release its adherence to the chuck and thereby avoid the difficulty ordinarily experienced in detaching such articles.

A modified form of the device is shown in Figs. 6 and 7. In this form the E type core 20 is enclosed in a relatively stationary casting 2|, suitably equipped with handles and lugs for fastening. The end profile of the central pole 22 is that of a concave cylinder surface. Coaxial with this surface is a laminated cylindrical roller 25 made from magnetic material and rotatably supported a slight distance from the pole by suitable bearings 23 secured to the core. Surrounding the pole and a portion of the roller is the energizing winding 24. A portion of the roller 26 furthest from the core 20 protrudes through an opening in the casing 2| and is tangent with the working plane of the device. In order to prevent entrance of foreign matter into the device the casing is equipped with leaf springs 25, the outer edges of which bear lightly against the roller throughout its length and thus produce a stripping action. The advantages and mode of operation with this form are in general similar to the device described in connection with Figs. 1 to 5.

Having thus described my invention and the advantages thereof I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim 1S! 1. In a device for removing residual magnetism, a laminated core, a pole on said core, the outer end of the pole having the contour of a cylindrical arc with the axis of the arc substantially at right angles to the laminating plane, and a winding on said pole for producing an alternating magnetic field beyond the outer end of the pole, said pole contour being adapted to be brought into close proximity with the surface to be demagnetized.

2. In a device for removing residual magnetism, a laminated core, a pole on said core, the outer end of the pole having the contour of a cylindrical arc, and a winding on said pole for producing an alternating magnetic field beyond the outer end of the pole, said pole contour being adapted to be brought into close proximity with the surface to be demagnetized.

3. In a device for removing residual magnetism, a source of alternating current, means connected with said source for producing an alternating magnetic flux, a relatively rotatable shell surrounding the flux producing means, said shell being adapted to furnish rolling contact with the surface from which residual magnetism is to be removed, and a means whereby a portion of the flux will traverse the shell.

4. In a device for removing residual magnetism, a laminated core, a winding on the core for producing an alternating magnetic circuit with a portion of the circuit external to the core, a relatively rotatable shell formed in a surface of revolution surrounding said core, and means whereby a portion of the demagnetizlng circuit will traverse a region outside the shell.

5. In a device for removing residual magnetism adapted for contacting engagement with the surface from which residual magnetism is to be removed, a laminated core, a pole on said core for producing a region of magnetic intensity in the contacting plane and a relatively rotatable cylinder between the pole and the plane of contact, rotation being imparted to said cylinder by relative motion of the demagnetizer and the surface treated.

6. A demagnetizer comprising a magnetic core, a cylindrical extension aflixed to each end of the core, a rotatable flange on each extension, at cylindrical shell seated at each end on one of said flanges and surrounding the core, and resilient means for pressing the flanges toward the core, whereby the shell is retained in seated engagement with said flanges.

'7. A device for removing residual magnetism comprising a laminated core, a winding on said core, a source of alternating current connected with said winding to produce an alternating flux in said core partially external to the core, a rela tively rotatable shell formed in a surface of revolution surrounding said core, and a means whereby a portion of the flux will traverse a region outside the shell.

8. In a device for removing residual magnetism, a laminated core, a pole integral with said core, the outer end of the pole having the contour of a cylindrical arc, a winding on the core to produce an alternating magnetic flux in said core and beyond the end of said pole, a relatively rotatable shell surrounding said core and winding, and means whereby a portion of the flux will traverse a region outside the shell.

9. In a device for removing residual magnetism adapted for contacting engagement with the surface to be demagnetized, the combination or a laminated core, a pole on said core for producing a region of magnetic intensity in the contacting plane, the face of said pole being of cylindrical contour, and a relatively rotatable cylinder between the pole and the plane of contact, said cylinder being substantially coaxial with said pole contour.

10. A portable device for removing residual magnetism adapted to contact with the surface to be demagnetized, comprising means for producing an alternating flux, a frame affixed to said flux producing means, a roller rotatably mounted on said frame and adapted to furnish said contact with said surface, and handles attached to said frame for moving the device in rolling engagement with said surface.

JOHN T. BEECI-ILYN. 

